Why your doctor is not an algorithm: exploring logical principles of different clinical inference methods using liver transplantation as a model. / Por qué mi médico no es un algoritmo? Fundamentos lógicos de los diferentes métodos de inferencia clínica a través del ejemplo del trasplante hepático.

The development of machine learning (ML) tools in many different medical settings is largely increasing. However, the use of the resulting algorithms in daily medical practice is still an unsolved challenge. We propose an epistemological approach (i.e., based on logical principles) to the application of computational tools in clinical practice. We rely on the classification of scientific inference into deductive, inductive, and abductive comparing the characteristics of ML tools with those derived from evidence-based medicine [EBM] and experience-based medicine, as paradigms of well-known methods for generation of knowledge. While we illustrate our arguments using liver transplantation as an example, this approach can be applied to other aspects of the specialty. Regarding EBM, it generates general knowledge that clinicians apply deductively, but the certainty of its conclusions is not guaranteed. In contrast, automatic algorithms primarily rely on inductive reasoning. Their design enables the integration of vast datasets and mitigates the emotional biases inherent in human induction. However, its poor capacity for abductive inference (a logical mechanism inherent to human clinical experience) constrains its performance in clinical settings characterized by uncertainty, where data are heterogeneous, results are highly influenced by context, or where prognostic factors can change rapidly.

CT-derived liver and spleen volume accurately diagnose clinically significant portal hypertension in patients with hepatocellular carcinoma.

Background & Aims: Clinically significant portal hypertension (CSPH) is a landmark in the natural history of cirrhosis, influencing clinical decisions in patients with hepatocellular carcinoma (HCC). Previous small series suggested that splanchnic volume measurements may predict portal hypertension. We aimed to evaluate whether volumetry obtained by standard multidetector computerised tomography (MDCT) can predict CSPH in patients with HCC. Methods: We included 175 patients with HCC, referred for hepatic venous pressure gradient (HVPG) evaluation, in whom contemporary MDCT was available. Liver volume, spleen volume (SV) and liver segmental volume ratio (LSVR: volume of the segments I-III/volume of the segments IV-VIII) were calculated semi-automatically from MDCT. Other non-invasive tests (NITs) were also employed. Results: Volume parameters could be measured in almost 100% of cases with an excellent inter-observer agreement (intraclass correlation coefficient >0.950). SV and LSVR were independently associated with CSPH (HVPG ≥10 mmHg) and did not interact with aetiology. The volume Index (VI), calculated as the product of SV and LSVR, predicted CSPH (AUC 0.83; 95% CI 0.77-0.89). Similar results were observed in an external cohort (n = 23) (AUC 0.87; 95% CI 0.69-1.00). Setting a sensitivity and specificity of 98%, VI could have avoided 35.9% of HVPG measurements. The accuracy of VI was similar to that of other NITs. VI also accurately predicted HVPG greater than 12, 14, 16 and 18 mmHg (AUC 0.81 [95% CI 0.74-0.88], 0.84 [95% CI 0.77-0.91], 0.85 [95% CI 0.77-0.92] and 0.87 [95% CI 0.79-0.94], respectively). Conclusions: Quantification of liver and spleen volumes by MDCT is a simple, accurate and reliable method of CSPH estimation in patients with compensated cirrhosis and HCC. Impact and implications: An increase in portal pressure strongly impacts outcomes after surgery in patients with early hepatocellular carcinoma (HCC). Direct measurement through hepatic vein catheterization remains the reference standard for portal pressure assessment, but its invasiveness limits its application. Therefore, we evaluated the ability of CT scan-based liver and spleen volume measurements to predict portal hypertension in patients with HCC. Our results indicate that the newly described index, based on quantification of liver and spleen volume, accurately predicts portal hypertension. These results suggest that a single imaging test may be used to diagnose and stage HCC, while providing an accurate estimation of portal hypertension, thus helping to stratify surgical risks.

Implementation and impact of an antibiotic control program and multidrug-resistant bacterial colonization in a liver transplant unit.

INTRODUCTION: infections by multidrug-resistant bacteria are a major cause of morbidity and mortality in transplant patients. OBJECTIVE: a retrospective single-center study was performed to evaluate the implementation of an Antimicrobial Treatment Optimization Program (PROA) on multidrug-resistant bacteria colonization and infection after liver transplant (LT). METHODS: colonization by multidrug-resistant bacteria and infections during the first year after a liver transplant were analyzed in a group of 76 transplanted patients in two stages, before and after PROA (2016-2019). Clinical variables related to infection, readmissions and survival one year after the liver transplant were analyzed. RESULTS: there was good adherence to the PROA. Infection was the most frequent cause for readmission during the first year after the liver transplant. Incidence of infections was similar during both periods (mean of 1.25 and 1.5 episodes of bacterial infection per patient/year, respectively) with 19 bacterial infectious episodes, six by hospital-acquired multidrug-resistant and extensively drug-resistant (MDR-XDR) bacteria in the pre-PROA stage, and 18 bacterial infectious episodes, five by MDR-XDR in the post-PROA stage. A 37 % decrease of post-TH of rectal colonization by MDR-XDR after liver transplant was observed during 2019. CONCLUSIONS: epidemiological surveillance policies and antibiotic optimization are key to control the increase of colonization and infection by multidrug-resistant bacteria in liver transplant units. Long-term studies are needed to better evaluate the impact of these programs.

Implantación e impacto de un programa de control antibiótico y colonización por bacterias multirresistentes en una unidad de trasplante hepático / Implementation and impact of an antibiotic control program and multidrug-resistant bacterial colonization in a liver transplant unit

Introducción: las infecciones por bacterias multirresistentes constituyen una importante causa de morbimortalidad pre coz en los pacientes trasplantados.Propósito: se presenta un estudio unicéntrico, retrospectivo, con objetivo de evaluar la implantación de un programa de optimización del uso de antibióticos y de control epidemio lógico (PROA) en la colonización e infección por bacterias multirresistentes tras el trasplante hepático (TH).Métodos: se analizaron la colonización por bacterias multi rresistentes y las infecciones en el primer año postrasplante hepático (post-TH) en un grupo de 76 pacientes trasplanta dos en dos etapas, anterior y posterior al PROA, entre los años 2016 y 2019. Se analizaron variables clínicas relacio nadas con infección, reingresos y supervivencia a un año.Resultados: se produjo una buena adherencia al PROA. Las infecciones en el primer año post-TH fueron la causa más fre cuente de reingreso. La incidencia de infecciones fue similar en ambos periodos, con una media de 1,25 y 1,5 episodios de infección bacteriana por paciente/año con 19 episodios infecciosos bacterianos, seis por bacterias multirresistentes y de resistencia extendida (MDR-XDR) en la etapa pre-PROA y 18 episodios infecciosos bacterianos, cinco por MDR-XDR. en la etapa posterior. Se objetivó un descenso del 37 % post TH de colonización rectal por MDR-XDR durante el año 2019.Conclusión: las políticas de vigilancia epidemiológica y optimización de antibióticos son necesarias como estrategia de control del incremento de colonización e infección por bac terias multirresistentes en unidades de trasplante hepático. Son necesarios estudios a largo plazo para evaluar mejor el impacto de estos programas (AU)

Liver and spleen volumes are associated with prognosis of compensated and decompensated cirrhosis and parallel its natural history.

OBJECTIVE: Cirrhosis is characterized by the complex interplay among biological, histological and haemodynamic events. Liver and spleen remodelling occur throughout its natural history, but the prognostic role of these volumetric changes is unclear. We evaluated the relationship between volumetric changes assessed by multidetector computerised tomography (MDCT) and landmark features of cirrhosis. METHODS: We included consecutive cirrhotic patients who underwent liver transplantation (LT) or hepatocellular carcinoma (HCC) resection in whom dynamic MDCT was available. Different volumetric indices were calculated. Fibrosis was evaluated by the collagen proportional area and Laennec sub-stages. Correlation and logistic regression analysis were performed to explore associations of volumetric indexes and fibrosis with key prognostic features across the clinical stages of cirrhosis. RESULTS: 185 patients were included (146 LT; 39 HCC); the predominant aetiology was viral hepatitis (51.35%); 65.9% had decompensated disease and 85.08% clinically significant portal hypertension (CSPH). The standardised liver volume and liver-spleen volume ratio negatively correlated with Model for End-stage Liver Disease (MELD), albumin and hepatic venous pressure gradient (HVPG) and were significantly lower in decompensated patients. The liver segmental volume ratio (segments I-III/segments IV-VIII) best captured the characteristic features of the compensated phase, showing a positive correlation with HVPG and a good discrimination between patients with and without CSPH and varices. Volumetric changes and fibrosis severity were independently associated with key prognostic events, with no association between these two parameters. CONCLUSIONS: Liver and spleen volumetric indices evolve differently along the natural history of cirrhosis and are associated with key prognostic factors in each phase, regardless of fibrosis severity and portal hypertension.

Decreased Long-Term Severe Acute Respiratory Syndrome Coronavirus 2-Specific Humoral Immunity in Liver Transplantation Recipients 12 Months After Coronavirus Disease 2019.

Long-term humoral immunity and its protective role in liver transplantation (LT) patients have not been elucidated. We performed a prospective multicenter study to assess the persistence of immunoglobulin G (IgG) antibodies in LT recipients 12 months after coronavirus disease 2019 (COVID-19). A total of 65 LT recipients were matched with 65 nontransplanted patients by a propensity score including variables with recognized impact on COVID-19. LT recipients showed a lower prevalence of anti-nucleocapsid (27.7% versus 49.2%; P = 0.02) and anti-spike IgG antibodies (88.2% versus 100.0%; P = 0.02) at 12 months. Lower index values of anti-nucleocapsid IgG antibodies were also observed in transplantation patients 1 year after COVID-19 (median, 0.49 [interquartile range, 0.15-1.40] versus 1.36 [interquartile range, 0.53-2.91]; P < 0.001). Vaccinated LT recipients showed higher antibody levels compared with unvaccinated patients (P < 0.001); antibody levels reached after vaccination were comparable to those observed in nontransplanted individuals (P = 0.70). In LT patients, a longer interval since transplantation (odds ratio, 1.10; 95% confidence interval, 1.01-1.20) was independently associated with persistence of anti-nucleocapsid IgG antibodies 1 year after infection. In conclusion, compared with nontransplanted patients, LT recipients show a lower long-term persistence of anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies. However, SARS-CoV-2 vaccination after COVID-19 in LT patients achieves a significant increase in antibody levels, comparable to that of nontransplanted patients.

HCV eradication in recurrent hepatitis C after liver transplantation normalizes enhanced endothelial activation.

The increased risk of cardiovascular disease (CVD) conferred by hepatitis C virus (HCV) is especially relevant after liver transplantation (LT), but its mechanism is still not well defined. This study aimed to evaluate the influence of HCV eradication in inflammatory and endothelial activation markers after LT. We evaluated inflammatory (TNF-alfa, IL-6, IL-8, and MCP-1) and endothelial activation (E-selectin, ICAM-1, VCAM-1, and MMP-9) markers before and after eradication in 45 LT recipients with HCV infection (LT+/HCV+) and 44 non-transplanted HCV-infected patients (LT-/HCV+). We also considered an additional group of 40 LT recipients without HCV infection (LT+/HCV-). LT+/HCV+ patients presented a higher endothelial activation status before eradication compared with LT+/HCV- patients. However, levels of E-selectin, ICAM-1, VCAM-1, and MMP-9 were comparable between LT+/HCV+ and LT-/HCV+ patients before eradication. HCV eradication decreased ICAM-1 (5466.55 pg/ml vs. 3354.88 pg/ml, P < 0.001) and VCAM-1 (10456.52 pg/ml vs. 6658.85 pg/ml, P < 0.001) levels in LT+/HCV+ and LT-/HCV+ patients. Remarkably, HCV eradication restored levels of endothelial activation markers of LT+/HCV+ patients compared with that of LT+/HCV- patients. HCV plays a major role in endothelial dysfunction after LT. Furthermore, HCV eradication restores endothelial activation despite the exposure to immunosuppressive therapy.

Regorafenib Efficacy After Sorafenib in Patients With Recurrent Hepatocellular Carcinoma After Liver Transplantation: A Retrospective Study.

Safety of regorafenib in hepatocellular carcinoma (HCC) recurrence after liver transplantation (LT) has been recently demonstrated. We aimed to assess the survival benefit of regorafenib compared with best supportive care (BSC) in LT patients after sorafenib discontinuation. This observational multicenter retrospective study included LT patients with HCC recurrence who discontinued first-line sorafenib. Group 1 comprised regorafenib-treated patients, whereas the control group was selected among patients treated with BSC due to unavailability of second-line options at the time of sorafenib discontinuation and who were sorafenib-tolerant progressors (group 2). Primary endpoint was overall survival (OS) of group 1 compared with group 2. Secondary endpoints were safety and OS of sequential treatment with sorafenib + regorafenib/BSC. Among 132 LT patients who discontinued sorafenib included in the study, 81 were sorafenib tolerant: 36 received regorafenib (group 1) and 45 (group 2) received BSC. Overall, 24 (67%) patients died in group 1 and 40 (89%) in group 2: the median OS was significantly longer in group 1 than in group 2 (13.1 versus 5.5 months; P < 0.01). Regorafenib treatment was an independent predictor of reduced mortality (hazard ratio, 0.37; 95% confidence interval [CI], 0.16-0.89; P = 0.02). Median treatment duration with regorafenib was 7.0 (95% CI, 5.5-8.5) months; regorafenib dose was reduced in 22 (61%) patients for adverse events and discontinued for tumor progression in 93% (n = 28). The median OS calculated from sorafenib start was 28.8 months (95% CI, 17.6-40.1) in group 1 versus 15.3 months (95% CI, 8.8-21.7) in group 2 (P < 0.01). Regorafenib is an effective second-line treatment after sorafenib in patients with HCC recurrence after LT.

Possible unrecognised liver injury is associated with mortality in critically ill COVID-19 patients.

BACKGROUND: Coronavirus disease (COVID-19) with acute respiratory distress syndrome is a life-threatening condition. A previous diagnosis of chronic liver disease is associated with poorer outcomes. Nevertheless, the impact of silent liver injury has not been investigated. We aimed to explore the association of pre-admission liver fibrosis indices with the prognosis of critically ill COVID-19 patients. METHODS: The work presented was an observational study in 214 patients with COVID-19 consecutively admitted to the intensive care unit (ICU). Pre-admission liver fibrosis indices were calculated. In-hospital mortality and predictive factors were explored with Kaplan-Meier and Cox regression analysis. RESULTS: The mean age was 59.58 (13.79) years; 16 patients (7.48%) had previously recognised chronic liver disease. Up to 78.84% of patients according to Forns, and 45.76% according to FIB-4, had more than minimal fibrosis. Fibrosis indices were higher in non-survivors [Forns: 6.04 (1.42) versus 4.99 (1.58), p < 0.001; FIB-4: 1.77 (1.17) versus 1.41 (0.91), p = 0.020)], but no differences were found in liver biochemistry parameters. Patients with any degree of fibrosis either by Forns or FIB-4 had a higher mortality, which increased according to the severity of fibrosis (p < 0.05 for both indexes). Both Forns [HR 1.41 (1.11-1.81); p = 0.006] and FIB-4 [HR 1.31 (0.99-1.72); p = 0.051] were independently related to survival after adjusting for the Charlson comorbidity index, APACHE II, and ferritin. CONCLUSION: Unrecognised liver fibrosis, assessed by serological tests prior to admission, is independently associated with a higher risk of death in patients with severe COVID-19 admitted to the ICU.

Changes in humoral immune response after SARS-CoV-2 infection in liver transplant recipients compared to immunocompetent patients.

The protective capacity and duration of humoral immunity after SARS-CoV-2 infection are not yet understood in solid organ transplant recipients. A prospective multicenter study was performed to evaluate the persistence of anti-nucleocapsid IgG antibodies in liver transplant recipients 6 months after coronavirus disease 2019 (COVID-19) resolution. A total of 71 liver transplant recipients were matched with 71 immunocompetent controls by a propensity score including variables with a well-known prognostic impact in COVID-19. Paired case-control serological data were also available in 62 liver transplant patients and 62 controls at month 3 after COVID-19. Liver transplant recipients showed a lower incidence of anti-nucleocapsid IgG antibodies at 3 months (77.4% vs. 100%, p < .001) and at 6 months (63.4% vs. 90.1%, p < .001). Lower levels of antibodies were also observed in liver transplant patients at 3 (p = .001) and 6 months (p < .001) after COVID-19. In transplant patients, female gender (OR = 13.49, 95% CI: 2.17-83.8), a longer interval since transplantation (OR = 1.19, 95% CI: 1.03-1.36), and therapy with renin-angiotensin-aldosterone system inhibitors (OR = 7.11, 95% CI: 1.47-34.50) were independently associated with persistence of antibodies beyond 6 months after COVID-19. Therefore, as compared with immunocompetent patients, liver transplant recipients show a lower prevalence of anti-SARS-CoV-2 antibodies and more pronounced antibody levels decline.

Long-term outcomes and clinical impact of anti-HLA donor-specific antibodies (DSA) after liver transplantation: a prospective study in a pilot cohort.

INTRODUCTION: the presence of donor-specific antibodies (DSA) is thought to affect survival of the allograft and patient after liver transplantation (LT). However, their significance is not well understood. PATIENTS AND METHODS: a prospective study was performed of 32 adult patients who underwent LT in 2011 to analyze the existence of DSA, associated risk factors and medium-term impact. Immunological determinations were performed immediately before LT and at three, six, 12 months and five years after LT. RESULTS: eight patients (24.2 %) presented pre-formed DSA. However, titers were negative in all patients five years after LT and there were no associated events. Eight out of 24 patients (33.3 %) developed de novo DSA. After five years, only two remained positive; both were class II with high mean fluorescence intensity (MFI) values at diagnosis (over 15,000). No association was found between the development of DSA and the risk of rejection, graft loss or death. However, an increase in liver stiffness values was observed in patients with persistent DSA, and focal sinusoidal deposition of C4d and moderate liver fibrosis were reported. CONCLUSION: the incidence of DSA is high after LT. In addition, the persistence of de novo DSA could be associated with silent liver fibrosis with a potential impact on graft outcomes.

Congenital Extrahepatic Portosystemic Shunts (Abernethy Malformation): An International Observational Study.

Congenital extrahepatic portosystemic shunt (CEPS) or Abernethy malformation is a rare condition in which splanchnic venous blood bypasses the liver draining directly into systemic circulation through a congenital shunt. Patients may develop hepatic encephalopathy (HE), pulmonary hypertension (PaHT), or liver tumors, among other complications. However, the actual incidence of such complications is unknown, mainly because of the lack of a protocolized approach to these patients. This study characterizes the clinical manifestations and outcome of a large cohort of CEPS patients with the aim of proposing a guide for their management. This is an observational, multicenter, international study. Sixty-six patients were included; median age at the end of follow-up was 30 years. Nineteen patients (28%) presented HE. Ten-, 20-, and 30-year HE incidence rates were 13%, 24%, and 28%, respectively. No clinical factors predicted HE. Twenty-five patients had benign nodular lesions. Ten patients developed adenomas (median age, 18 years), and another 8 developed HCC (median age, 39 years). Of 10 patients with dyspnea, PaHT was diagnosed in 8 and hepatopulmonary syndrome in 2. Pulmonary complications were only screened for in 19 asymptomatic patients, and PaHT was identified in 2. Six patients underwent liver transplantation for hepatocellular carcinoma or adenoma. Shunt closure was performed in 15 patients with improvement/stability/cure of CEPS manifestations. Conclusion: CEPS patients may develop severe complications. Screening for asymptomatic complications and close surveillance is needed. Shunt closure should be considered both as a therapeutic and prophylactic approach.

Clinical Utility of a Risk-Adapted Protocol for the Evaluation of Coronary Artery Disease in Liver Transplant Recipients.

The prevalence and management of coronary artery disease (CAD) in liver transplantation (LT) candidates are not well characterized. The aims of this study were to evaluate the impact on clinical outcomes of a specifically designed protocol for the management of asymptomatic CAD in LT candidates and to investigate noninvasive risk profiles for obstructive and nonobstructive CAD for 202 LT candidates. Those with high baseline cardiovascular risk (CVR; defined by the presence of classic CVR factors and/or decreased ejection fraction) received coronary angiography and significant arterial stenosis and were treated with percutaneous stents. Patients were followed up after LT until death or coronary event (CE). There were 78 patients who received coronary evaluation (62 direct angiography, 14 computed tomography coronary angiography, and 2 both). Of them, 39 (50%) patients had CAD of any severity, and 6 (7.7%) had significant lesions (5 were amenable to be treated with stents, whereas 1 patient had diffuse lesions which contraindicated the LT). Insulin-dependent diabetes was the only factor related to CAD of any severity (odds ratio, 3.44; 95% confidence interval [CI], 1.00-11.97). A total of 69 patients (46 with coronary evaluation) received LT. The incidence of CEs and overall survival after LT were similar between patients with and without coronary evaluation. Furthermore, no differences occurred between these groups in a multivariate competing risk model (subhazard ratio, 0.84; 95% CI, 0.27-2.61; P = 0.76). In conclusion, the application of an angiographic screening protocol of CAD in a selected high-risk Mediterranean population is safe and effective. The short- and medium-term incidence rates of CEs and death after LT in this population are similar to that observed in low-risk patients.